Conventional light transmission systems used for vehicle lighting, including vehicle tail lights, typically use a bulb and reflector system. In a bulb and reflector system, the filament of the bulb is placed at or near a focal point of a parabolic reflector. The light emitted by the bulb filament is collected by the reflector and reflected outward to form a light beam. A lens is used to shape the light beam into a specified pattern to satisfy vehicle lighting specifications. Typically, in an automotive application, a conventional bulb and reflector system collects and reflects only thirty percent of the light emitted from the bulb filament into the useful lighting area.
Bulb and reflector systems have several disadvantages, including aerodynamics and aesthetic styling. For example, the depth of the reflector along its focal axis and the height of the reflector in directions perpendicular to the focal axis greatly limited attempts at streamlining vehicle contours. Additionally, thermal energy given off by the bulb during operation must be dissipated so that the size of the reflector as well as the material used in its construction are additional factors complicating vehicle design with conventional lighting systems.
One approach to develop an automotive lighting system for use with streamlined body designs is proposed in U.S. Pat. No. 5,434,754, assigned to the assignee of the present invention, which discloses the combination of a fiber optic light guide which transmits light from a remote light source, through a light manifold, and to a reflector. Another approach, as shown in U.S. Pat. No. 5,700,078, also assigned to the assignee of the present invention, includes a remote laser light source coupled with a light transmitting fiber optic light pipe which illuminates a unitary thin sheet optic having an input section, a manifold sections, and a kicker section. While these approaches significantly advanced the state-of-the-art in vehicle design by eliminating bulky and inefficient reflectors and bulbs, the need for providing multiple colors for rear lighting requirements still remains.
This need, which is a further complicating factor in designing vehicle lighting systems, is for two or more colors to emanate from a single taillight assembly or from the same general area on the rear of a vehicle. Typically, a vehicle taillight assembly includes a taillight having a red lens for rear illumination and braking, a blinker having a yellow lens, and a backup light having a clear or white lens. Each of these usually requires a separate lens for covering a separate bulb and reflector system, thus increasing system cost and complexity.
One approach to the multi-color lighting problem is described in U.S. Pat. No. 5,136,483, which shows an illuminating element with a circumferential edge in which a plurality of LEDs are placed. The LEDs may be of various colors so that illumination of some, or all, may produce various colors. A drawback of this design, however, is the lack of ability to simultaneously illuminate separate portions of the light with two or more different colors. In the designs disclosed in U.S. Pat. No. 5,570,951 and U.S. Pat. No. 5,477,436, a plurality of light sources emit light of only one color through lens sections, or covers, which mix the colors to produce a uniform color. There is no provision to produce multiple colors through individual sections of the light for various lighting functions, however.
Therefore, it would be desirable to provide a taillight assembly for a vehicle which accommodates manufacturing and thermal considerations as well as the space limitations dictated by vehicular aerodynamic and styling requirements, and which provides multiple functions, such as rear illumination, brake lighting, backup lighting, or other signaling, without use of multiple lens.